We often talk about anthracnose on trees. Most of us have heard of sycamore anthracnose, and in Illinois we see anthracnose in the spring on ash, oak, maple, and walnut. Anthracnose diseases occur on many plants, including trees, shrubs, field crops, fruit, turf, vegetable, and even perennials. Anthracnose diseases are caused by various fungi that produce their spores in a fungal fruiting body called an acervulus. The acervuli (plural) are often visible as small dark dots in the necrotic leaf or stem lesions, and the spores are often released in slimy masses.|
Anthracnose symptoms typically appear as dark-colored spots or sunken lesions that can quickly run together to form irregular dark lesions that cause rapid blighting of leaves or stems. This blighting can result in severe plant losses if not diagnosed in the early stages of infection. Under wet conditions anthracnose can have multiple infection cycles during the growing season.
Perennials commonly infected by anthracnose diseases include acorus, bellamcanda, bergenia, calamagrostis, convallaria, dianthus, epimedium, heuchera, hosta, liatris, liriope, luzula, malva, miscanthus, panicum, pennisetum, phlox, polygonatum, rudbeckia, saponaria, sedum, and tiarella.
Anthracnose diseases are manageable. They can be controlled and do not require removal of the infected plants. If possible, water plants early in the day, allowing leaves to dry before evening. Keeping foliage dry overnight helps prevent fungal diseases, because infection usually occurs when leaves are wet for prolonged periods. Pick and discard infected leaves and stems, working only with dry plants. Cut the infected plant to the ground level in the fall, and discard foliage in the trash rather than composting. Thorough fall cleanup of plant residue will help reduce the amount of infection the next growing season. Many fungicide options are listed in the Home, Yard, and Garden Pest Guide and the Commercial Landscape and Turfgrass Pest Management Handbook, both available from http://www.PublicationsPlus.uiuc.edu. Recommendations are preventives, used to protect nearby plants or those known to have had past problems. Products are listed by host plant.